The present invention relates generally to the field of biomedicine and biotechnology, and more particularly, to cell-based devices such as bioartificial liver or bioartificial kidney and blood therapy devices such as hemodialysis or hemofiltration system and methods therefore. Although the invention is subject to a wide range of applications, it is especially made suited for use as an extracorporeal blood therapy device with multiple functions integrated in a single module and will be particularly described in that connection.
Various reactors, bioreactors, modules and cartridges (xe2x80x9cBIOREACTORSxe2x80x9d) used as cell culture devices and extracorporeal blood therapy devices [xe2x80x9c(BIO)ARTIFICIAL ORGANSxe2x80x9d] are known. Typically, the known bioreactors utilize hollow-fiber technology. An array of single and dual hollow-fiber reactors exists and their fabrication and application are well known in the prior art as shown by the teachings of U.S. Pat. Nos. 3,442,002; 3,492,698; 3,821,087; 3,883,393, 4,184,922; 4,219,426; 4,220,725; 4,226,378; 4,276,687; 4,283,284; 4,329,229; 4,334,993; 4,361,481; 4,374,802; 4,389,363; 4,647,539; 5,015,585; 5,605,835, 5,712,154 and other related patents.
In a single hollow-fiber bioreactor, a bundle of small-diameter porous hollow fibers are contained in a housing that is rigid and sealed. The bundle of fibers is stretched so that the individual fibers run in parallel to each other. The ends of the bundle are sealed at each end so that two compartments are formed: intrafiber that is within the lumens of the fibers and extrafiber that is outside the fibers but still within the housing. In a dual hollow-fiber bioreactor, two separate bundles of small-diameter porous hollow fibers are contained in a common housing so that three compartments are formed and each compartment has its own inlet and outlet ports.
Applications range from the filtration, purification and reclamation of industrial waste products to highly sophisticated biomedical applications in the Health Sciences Field. These include, but are not limited to, the exchange and mass transfer of dissolved gases and aqueous solutions of typical applications such as hemodialysis, plasma separation, extracorporeal gas exchange, process filtration of pharmaceutical solutions, extracorporeal cell-based artificial organs such as bioartificial livers, and the cultivation and expansion of mammalian and plant cells in bioreactors (U.S. Pat. No. 3,883,393 and other related patents).
The teachings of the above prior art have many shortcomings. The principal shortcoming of single hollow-fiber bioreactor is its inability to perform more than one operation at a time. As result, oxygenation of cells medium has to be provided externally. Moreover, in all hollow-fiber bioreactors (single, dual), mass transport across the fiber wall occurs primarily by diffusion, and the nutrient medium is also the production medium. In addition, the fibers may splay apart from one another when the bundle is sealed in the shell, increasing the possibility that cells between the fibers may be anoxic. The principal drawback of a dual circuit hollow-fiber bioreactor by Knazek et al (U.S. Pat. No. 4,184,922) and by Mullon et al. (U.S. Pat. No. 5,712,154) is that their construction does not guarantee uniform distribution of both sets of fibers (e.g., source or nutrient fibers and sink or production fibers). Cells may preferentially grow on or near the source fibers. In addition, if the second set of fibers is used for bleed-off of concentrated product (sink fibers), the nutrient medium must be oxygenated externally. If, in turn, one of the sets of fibers is used for oxygen delivery, then the nutrient medium is also the production medium, as in a single-fiber module.
A dual hollow-fiber cell culture devices with a tube-within-a-tube configuration had been described by Channing R. Robertson and In Ho Kim in 1985, by Linda Custer in 1988 and by James R. Robinson in 1991 (U.S. Pat. No. 5,015,585). In all instances, the intent of an inventor or author was to place a biological component in annular spaces formed between the inner and outer tubes, to use inner tubes for integrated oxygenation and/or to use them as source or nutrient fibers, and to use the space outside the outer fibers as either a sink or a second passage of fluidized nutrients. Though these devices represented a major improvement, they have certain drawbacks, because when used as a cell culture device or a bioartificial organ, the annular space thickness would have to be relatively thin (on the order of 200 microns as stated in the U.S. Pat. No. 5,015,585) to ensure adequate oxygenation and nutrition of cells. A bioreactor with fiber pairs having such a narrow annular space would have to be very large to accommodate sufficient number of cells to provide enough function. In addition, loading of cells would be very difficult. As a consequence of these drawbacks, none of the aforementioned designs resulted in the development of a commercially viable product.
A need therefore exists for a multi-compartment bioreactor, and a method therefor, that allows integration of at least two functions in a single module and, at the same time, loading and maintenance of large number of viable functional cells.
The invention, which tends to address this need, resides in a bioreactor. The bioreactor described herein provides advantages over known bioreactors in that it integrates in a single module at least two independent operations (e.g., functions, modes of therapy).
According to the present invention, the foregoing advantage is principally provided by the employment of a three-compartment module whereby the cell (animal, human, plant, insect) can be populated and expanded in an outer (shell) compartment (C1), while circulating a medium (culture medium, blood or plasma) coaxially within the second mid (e.g., annular) compartment (C2) and circulating fluid (e.g., gaseous medium, plasma) within the third inner compartment (C3) adjacent to the C2 compartment. Due to the presence of these three compartments and the proposed method of use thereof, a bioartificial organ (e.g., liver, kidney, pancreas, thyroid, parathyroid, adrenal, etc.) can be constructed, where two different functions (e.g., cell therapy and oxygenation, cell therapy and blood/plasma dialysis or ultrafiltration or diafiltration or any other form of therapy, including regional delivery of pharmacological agents) are integrated in a single module.
In the configuration using hollow fibers, the bioreactor is comprised of a plurality of two hollow fiber bundles, each said hollow fiber bundle interdependent of the other whereby each individual hollow fiber, comprising the plurality of hollow fibers in one bundle, is disposed coaxially inside each hollow fiber of the other hollow fiber bundle. A large number of pairs of hollow fibers are useful such as several hundred pairs.
In accordance with one aspect of this invention, the composite bundle of hollow fibers-within-hollow-fibers is further disposed in a generally rigid, tubular housing having diametrically enlarged double manifolds members adjacent opposite housing ends. Said tubular housing disposes a third compartment enclosing the concentrically arranged fiber-within-a-fiber bundle.
In accordance with another aspect of this invention, relatively resilient plastic sleeve members are carried at each end of each interdependent hollow fiber bundle and the tubular housing; said plastic sleeve members are sealed diametrically opposed to each fiber bundle and the housing member. Preferably, the sleeves are made from a material which sealingly adheres to the each individual hollow fiber and tubular housing to facilitate a hermetic seal of the system. Thus, the three compartments are coaxially disposed yet separate and independent.
In accordance with another aspect of this invention, each of the three compartments has its own inlet and outlet port.
In accordance with another aspect of this invention, the module can be populated with hydrophobic or hydrophilic hollow fibers or a combination thereof.
In accordance with another aspect of this invention, the module can be populated with surface modified membranes for specific applications; for example, membranes with anti-fouling and/or anti-thrombogenic properties with enhanced bio- and/or blood compatibility.
In accordance with another aspect of this invention, it is critical to consider the appropriate spacing (compartment size) between the inner fiber and the concentric outer fiber and the relative size of one hollow fiber to the other and the overall diameter of the tubular housing. The size of the innermost hollow fiber may preferably range from an internal diameter (I.D.) between 100 microns and 1000 microns and a wall thickness of 50 to 100 microns. The axially and concentrically placed outer hollow fiber size would preferably range in size from an internal diameter of 300 microns and a wall thickness of at least 50 microns to an external diameter of 2,000 microns or more. The overall functional surface area (S.A.) of a suitable module will depend on its specific application. The S.A. can range from a few centimeter square to 200 meter square or more. The range of space between OD of inner fiber and ID of outer fiber can range from 50 microns to 1000 microns or more.
It is another aspect of this invention to use one or a combination of hollow fibers with molecular weight cut off""s (MWCO) for tailor-made applications (e.g., oxygenation, immunoisolation of cells, collection of substances with specific molecular weights) and/or using one or all of the hollow fiber sizes utilized in the fabrication of a module.
In accordance with another aspect of this invention, the materials used for the inner fiber and/or the outer fiber is preferably a microporous hollow fiber. A preferred range of porosity of from 0.10 microns to 5.0 microns help maintain excellent cell survival, function and proliferation. A 0.2 micron microporous mixed ester cellulose hollow fiber containing bioreactor worked successfully in testing. The use of such microporous hollow fibers allows a greater range of spacing than does the low molecular weight polypropylene suggested in Robinson U.S. Pat. No. 5,015,585.
In accordance with the method of this invention, a bioartificial liver is constructed where the liver cells are placed in the extrafiber (shell) compartment, the annular space in between the fibers is perfused with whole blood or plasma, and the inner fibers are used for blood purification therapy by means of either dialysis or ultrafiltration or diafiltration.
In accordance with the method of this invention, a bioartificial liver is constructed where the liver cells are placed in the extrafiber (shell) compartment, the annular space in between the fibers is perfused with whole blood or plasma, and the inner fibers are used for oxygenation of blood/plasma which is pumped through the annular spaces between the two fiber systems.
In accordance with the method of this invention, the fluid circulated through the inner fibers of a bioartificial liver can be a standard hemodialysis fluid, an albumin-enriched solution, a human fresh frozen plasma, or any other suitable fluid.
In accordance with the method of this invention, a bioartificial kidney is constructed where the renal cells are placed in the extrafiber (shell) compartment, the annular space in between the fibers is perfused with whole blood or plasma, and the inner fibers are used for blood purification therapy by means of either dialysis or ultrafiltration or diafiltration.
In accordance with the method of this invention, the porosity of the inner and outer fiber walls are judiciously chosen so as to use the annular space for passage of blood or plasma and both adjacent compartments for enhanced blood purification therapy, i.e., dialysis, ultrafiltration, diafiltration, drug delivery or any combination thereof. In accordance with this method of the invention, the fluid circulated through the spaces adjacent to the annular space (outer fiber compartment and inner fiber compartment) can be a standard hemodialysis fluid, an albumin enriched solution, a human fresh frozen plasma, or any other suitable fluid. Thus, in accordance with this method of the invention cell therapy is not used at all and the module functions as an interface for two different blood therapies (e.g., hemodialysis and hemodiafiltration).
In accordance with the method of this invention, the porosity of the inner fiber wall in a bioartificial liver is adjusted to specific mode of blood purification therapy, i.e., dialysis, ultrafiltration, or diafiltration.
It is to be understood by those skilled in the art that the above description and general specifications are merely for illustrative purposes and shall in no way limit the range of specifications suitable for use in the three-compartment hollow fiber or flat-bed module.